1. Field of the Invention
The present invention concerns a chain saw equipped with a device for adjusting the tightness of the cutting chain.
2. Description of Related Art
Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Such chain cutting tools are usually called chain saws and are commonly used to cut various materials (wood, concrete, bricks, tiles, etc.). They include a cutting device constituted by an endless cutting chain turning around a drive sprocket and a chain guide generally of an oblong shape and equipped with a peripheral guide bar and a power source for the drive of this chain by means of said sprocket. To perform a satisfactory and safe job, it is indispensable for the chain to be perfectly tensioned. As a matter of fact, when this chain is loose, it represents a major risk of jumping off the sprocket and breaking, thereby putting the operator at risk of injury. On the other hand, when the chain is too tight, this results in faster wear of the chain and the guide bar, abnormal overheating of both the chain and the guide bar, higher energy consumption and loss of efficiency of the cutting device that could lead to its seizing up.
On account of the fact that the chain slackens by itself due to the wear of the chain pins while the chain is in use, adjustment of its tension cannot be made once and for all but must instead be repeated regularly, whenever said chain becomes loose. This is a delicate and complicated operation because it is difficult for the operator to determine and to obtain the tension that is just right.
Numerous devices have been offered to date for adjusting the tension of the cutting chain, which requires removal of the guide bar which tends to move further away from the drive sprocket. However, none of these devices permits a satisfactory automatic adjustment of this tension. In general the adjustment principle for the tension means actuating a tensioning device parallel to the guide bar.
These known devices require much experience to obtain an adjustment to the proper tension, and, in spite of such experience, a good adjustment is not always assured.